Four degrees and beyond: the potential for a global ... - Amper

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Rethinking adaptation for a +4 ◦ C world 211
max water-level rise: top of likely range for 2100 top of extreme high
scenario for 2100
existing system
raise defences
over-rotate Thames
Barrier and restore
interim defences
1 m 2 m 3 m 4 m
improve Thames Barrier and raise downstream defences
flood storage, over-rotate Thames
Barrier, raise upstream and
downstream defences
flood storage, restore
interim defences
new barrier, retain Thames Barrier, raise defences
new barrier, raise defences
new barrage
flood storage, improve Thames
Barrier, raise upstream and
downstream defences
Figure 3. Adaptation options and a decision pathway for flood risk management in the Thames
Estuary. The dashed lines indicate the extents of water-level rise projected for 2100 under different
scenarios. The thick grey line shows one possible pathway for introducing different options to
address rising water levels. This type of flexible pathway shows how incremental and transformative
options can be combined. Adapted from Lowe et al. ([54], fig. 7.4). Boxes indicate measures for
managing flood risk indicating effective range against water level.
can be adapted to the rate of change that eventuates. Planning decision lead times
and consequence times created challenges, which were also explicitly addressed,
with the timing of key decision points identified along the trajectory.
The TE2100 options were the subject of extensive stakeholder engagement,
and subsequently formed the basis of the draft plan awaiting UK government
approval in early 2010. In line with UK government guidance on climate change
at the time, the plan focuses on a potential 1mwater-level rise over 100 years. It
identifies the appropriate pathway to address that level of change, with actions
for the short (to 2034), medium (to 2069) and long term (from 2070). Thus, the
plan itself defines a set of incremental adaptation measures, rather than explicitly
documenting the complexity of the underlying research. However, three important
elements distinguish this approach from previous incremental analyses.
— Shorter term decisions are nested within a longer term framework that
explicitly identifies key thresholds and options for dealing with much
larger extents of change. (For example, 10 indicators for change will be
formally monitored to identify if or when a switch to alternative options
may be needed.)
— The plan allows for flexibility on the timing of introduction of different
options and interventions, and the ability of the plan to change between
options, based on the monitoring programme.
Phil. Trans. R. Soc. A (2011)
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